Flame retardancy and dielectric properties of dicyclopentadiene‐based benzoxazine cured with a phosphorus‐containing phenolic resin

Abstract

A dicyclopentadiene-based benzoxazine (DCPDBZ) was prepared and separately copolymerized with melamine-phenol formaldehyde novolac or phosphorus-containing phenolic resin (phosphorus-containing diphenol) at various molar ratios. Their curing behaviors were characterized by differential scanning calorimetry. The electrical properties of the cured resins were studied with a dielectric analyzer. The glass-transition temperatures were measured by dynamic mechanical analysis. The thermal stability and flame retardancy were determined by thermogravimetric analysis and a UL-94 vertical test. These data were compared with those of bisphenol A benzoxazine and 4,4 0 -biphenol benzoxazine systems. The effects of the diphenol structure and cured composition on the dielectric properties, moisture resistance, glass-transition temperature, thermal stability, and flame retardancy are discussed. The DCPDBZ copolymerized with phosphorus-containing novolac exhibited better dielectric properties, moisture resistance, and flame retardancy than those of the melamine-modified system. The flame retardancy of the cured benzoxazine/phosphorus-containing phenolic resins increased with increasing phosphorus content. The results indicate that the bisphenol A and 4,4 0 -biphenol systems with a phosphorus content of about 0.6% and the dicyclopentadiene system with a phosphorus content of about 0.8% could achieve a flame-retardancy rating of UL-94 V-0.

Preparation and properties of novel low dielectric constant benzoxazole‐based polybenzoxazine

“…The dipole does not follow the alternating field. Figure 14 also suggests that unlike the dielectric constant of common polybenzoxazine, which strongly depends on temperature,37 the dielectric constants of poly(DAROH‐a) at the same frequency barely change under low temperatures up to 150 °C.…”

“…The excitation wavelength is 353 nm. The poly(DAROH‐a) film displays a strong PL emission peak at 521 nm, which has a slight red shift compared with the emission of benzobisoxazole chromophore units 37. The possible reason for this red shift is the incorporation of benzoxazine rings to benzobisoxazole, which might hinder the aggregation of benzobisoxazole groups.…”

“…Many reports on benzoxazine have been published in recent years. The majority of studies reported have focused on synthesis methods,5 polymerization,15,16 blending and composites,17–19 properties,20,21 and reaction mechanisms22,23 of benzoxazine monomers and the resultant polymers. Many chemical groups have been incorporated in benzoxazine monomers to improve the properties of benzoxazines and polybenzoxazines.…”

Flame retardancy working mechanism of methyl‐DOPO and MPPP in flexible polyurethane foam

“…DOPO (9, 10‐dihydro‐9‐oxa‐phosphaphenthren‐10‐oxide) was first synthesized by Saito 10 in 1978 and is nowadays applied in electrical/electronic cast resins and polyester fibers 11–17. The FR mechanism of DOPO and its derivatives is explained by the release of low molecular weight phosphorus‐containing species that are able to scavenge the H‐ and OH‐radicals in the flame 18.…”

A facile way to prepare two novel DOPO‐containing liquid benzoxazines and their graphene oxide composites

“…Various kinds of additive and reactive flame retardants containing phosphorus are increasingly potential for halogen‐free to replace halogenated flame retardants for different polymeric materials and applications . Phosphorus can work in the condensed phase by improving charring, yielding intumescences, or through inorganic glass formation; and in the gas phase through flame inhibition . According to reported in the literature, occurrence and efficiency of flame retardance depend, not only on the flame retardant itself, but also on its interaction with pyrolyzing polymeric material and additives .…”